Exchange bias system of Fe/KFeF3

Epitaxial Fe/KFeF3 bilayers were grown using molecular beam epitaxy on GaAs (100). FMR measurements revealed two peaks for samples with an Fe seed layer. A peak with fourfold symmetry was identified as the main layer Fe whereas a peak with twofold symmetry appeared to be due to the seed layer Fe. The magnetocrystalline anisotropy for the fourfold peak is similar to400 Oe at 300 K whereas a large anisotropy of 1.5 kOe is associated with the seed layer. A large rotatable anisotropy of 280+/-20 Oe was found for a sample with Fe thickness 2.1 nm. All Fe/KFeF3 bilayers checked by superconducting quantum interference device exhibit exchange bias and enhanced coercivity. The blocking temperature of the system is close to the Neel temperature 112 K of KFeF3. One sample has polycrystalline KFeF3 and shows a much larger exchange bias and coercivity than the samples having single crystal KFeF3. (C) 2004 American Institute of Physics.